The present invention relates to a parking brake device mounted on a vehicle, and more particularly to a parking brake device using a brake cable.
FIGS. 5A and 5B show an example of prior art parking brake device. A parking brake device 80 mounted on a forklift truck includes a lever bracket 81, a brake lever 82, a brake mechanism 86 and a brake cable 83. The lever bracket 81 is fixedly located near a driver seat of a body of the vehicle. The brake lever 82 is tiltably supported by the lever bracket 81 and has an actuating portion at one end. The brake mechanism 86 controls rotation of a drive system shaft member in the vehicle body. The brake cable 83 operates the brake mechanism 86 by tilting motion of the brake lever 82.
In the above parking brake device 80, the brake lever 82 and the brake mechanism 86 are connected by the brake cable 83 in such a manner that a braking state and a releasing state of the brake mechanism 86 are switched by the tilting motion of the brake lever 82. The brake cable 83 generally includes a cylindrical outer casing 84 and an inner cable 85 which extends through the outer casing 84. The outer casing 84 is mounted on the vehicle body, such as the lever bracket 81 and the bracket near the brake mechanism 86. One end of the inner cable 85 is held by the brake lever 82 and the other end thereof is held by a lever 87 of the brake mechanism 86. In this structure, the inner cable 85 is slidably moved along the outer casing 84 by the tilting motion of the brake lever 82 thereby to pull the lever 87, with the result that the brake mechanism 86 becomes the braking state.
FIG. 6 shows another example of prior art parking brake device. A parking brake device 90 includes a brake mechanism having brake portions provided near right and left wheels, respectively. For the sake of convenience, only a brake portion 98 near the left wheel is shown in FIG. 6 and the other brake portion near the right wheel is not shown. The parking brake device 90 is so formed that a braking state and a releasing state of each brake portion are switched simultaneously on both right and left sides by tilting motion of a brake lever 92 of a lever bracket 91. Thus, two brake cables 93, each of which has an outer casing 94 and an inner cable 95, are used in the parking brake device 90. Specifically, the parking brake device 90 includes a link member 96 and an equalizer member 97. One end of the link member 96 is connected to the brake lever 92 and the other end thereof is connected to the equalizer member 97 which holds the ends of the inner cables 95.
The other ends of the inner cables 95 which are connected to the equalizer member 97 are distributed into the right and left brake portions. For example, one of the inner cables 95 is connected to a lever 99 of the left brake portion 98. One end of each outer casing 94 is fixed to the lever bracket 91 and the other end thereof is fixed to a bracket near the corresponding brake portion. For example, one of the outer casings 94 is connected to a bracket 100 of the left brake portion 98. Since the two brake cables 93 are the same structure, the right and left brake portions are simultaneously operated through the two brake cables 93 by the tilting motion of the brake lever 92.
In the above parking brake devices, when tensile force is exerted on the brake cable, while the inner cable of the brake cable tends to elongate, the outer casing of the brake cable tends to shrink. Therefore, when the inner cable is pulled, for example, by tilting motion of the cable lever, pull length of the inner cable on the brake lever side does not coincide with that of the inner cable on the brake mechanism side. Specifically, the pull length of the inner cable on the brake mechanism side is reduced thus causing stroke loss of the pull length. In particular, when the pull length of the inner cable caused by tilting motion of the brake lever is set at a predetermined length as in the case of toggle type brake lever, a remarkable increase of the stroke loss causes the pull length of the inner cable needed for operating the brake mechanism to be reduced. Therefore, there is fear that the parking brake device may not function normally.
Meanwhile, for example, in a brake mechanism of a drum brake having a clearance between its brake drum and its brake shoe, pull length of an inner cable of the brake cable is distributed into a range in which the brake shoe fills up the clearance to be brought into contact with the brake drum and a range in which the brake shoe applies load to the brake drum after being brought in contact with the brake drum. When the pull length of the inner cable is set at a predetermined length, the above stroke loss reduces the clearance between the brake shoe and the brake drum. To cancel the stroke loss, the rigidity of the brake cable is conventionally enhanced by merely increasing the diameter of the brake cable.
Japanese Patent Application Publication (KOKAI) No. 2004-230986 discloses an auxiliary brake device for a parking brake device. This auxiliary brake device includes an auxiliary brake pedal supported by an operation bracket on a passenger seat side and a lever supported by an operation bracket on a driver seat side for pushing another brake pedal. Additionally, the auxiliary brake device includes transmission means for transmitting force for pushing the auxiliary brake pedal to the above lever. The transmission means includes two cables which are juxtaposed to each other. The auxiliary brake device is so formed that the brake pedal is pushed through the cables and the lever by pushing the auxiliary brake pedal.
When the diameter of each brake cable of the above parking brake devices is increased, however, there is a problem that installation space needed for disposing the brake cable is increased. Depending on the type of the vehicle, the installation space for disposing the brake cable having relatively large diameter may not be sufficiently ensured. When the diameter of the brake cable is increased to enhance the rigidity of the brake cable, it becomes hard to bend the brake cable. For example, operation for bending the brake cable to dispose the brake cable in the vehicle body tends to be hindered.
Although the above auxiliary brake device uses a plurality of brake cables to enhance the rigidity in the entirety of the brake cables without increasing the diameter of each brake cable, the auxiliary brake device does not disclose the brake cables which connect a brake portion with a brake lever. In other words, the auxiliary brake device merely discloses two cables for transmitting force for pushing the auxiliary brake pedal to the lever. In addition, when pull length of the brake cable is set at a predetermined length, the auxiliary brake device does not disclose the solution of the problem on a brake mechanism side caused by stroke loss.